1. Field of the Invention
The present invention relates to an electrically operated transmission gear system for use on a bicycle, and more particularly to such a transmission gear system for automatically selecting a transmission gear best suited for the speed of travel of the bicycle and/or the speed of rotation of a crank gear. The present invention is also concerned with a bicycle equipped with such an electrically operated transmission gear system.
2. Prior Art
There has been known a transmission gear system with electrically controlled gearshifting, as disclosed in U.S. Pat. No. 4,143,557, patented Mar. 13, 1979. The transmission gear system includes a manually operated switch mounted on a handle of a bicycle for electrically actuating a gearshifting means for the transmission gears. With the disclosed system, selection of a transmission gear is up to the rider of the bicycle, who is required to determine a desired transmission gear while taking into consideration the speed at which the bicycle runs and other factors. There is a tendency, however, for the bicycle rider to fail under various conditions to pick out an optimum transmission gear for the speed of travel of the bicycle.
One known arrangement to let the rider know a proper transmission gear for the speed at which the bicycle is running comprises a speedometer including an indication of transmission gears as related to bicycle speeds. This conventional arrangement, however, requires the rider first to confirm an optimum transmission gear corresponding to the speed as indicated on the speedometer, then to determine whether to change gears up or down, and finally to operate the transmission gear system to reach a desired gear. Such a procedure distracts the rider's attention from driving, rendering the bicycle riding less safe on the road.